1. Field of the Invention
The present invention relates to the field of burners and combustion systems, and more specifically, to reburning apparatus used in NO.sub.x reduction in cyclone fired boilers.
2. Description of the Related Art
NO.sub.x reduction in cyclone fired boilers using "reburning" is a technology that has been developing over the past several years. Starting with bench scale testing in the 1980's, the technology has progressed to the full scale demonstration stage with recent tests using pulverized coal and natural gas as reburn fuels. The current technology utilizes separate reburn fuel injection ports or burners to introduce the reburn fuel in the lower furnace region, along with a set of overfire air ports located in the mid to upper portion of the furnace to admit combustion air. The furnace region between the reburn fuel ports and the overfire air ports is the reburn zone where substoichiometric conditions reduce the NO.sub.x that is created in the cyclones to elemental Nitrogen.
U.S. Pat. No. 2,546,937 discloses a retractable lance for use in a steel furnace. The lance is disclosed as being retractably mounted through a wall of a furnace.
U.S. Pat. No. 2,485,656 discloses a hydroxilating fuel burner comprising a adjustable fuel injecting lance contained within a cyclone type furnace region with an adjustable shell around it. The outer shell around the lance is adjustable to constrain the airflow around and into the fuel injection area. The '656 patent is disclosed as being primarily an oil fuel gun for use in a furnace, however, the patent also disclosed its potential use for pulverized coal or natural gas.
U.S. Pat. No. 4,924,784 discloses a cooling water system for a fuel lance. The '784 patent teaches a jacket-cooled fuel pipe with separate cooling water sources for various parts of the fuel lance for use in a boiler.
In U.S. Pat. No. 5,022,329 a hazardous waste incinerator incorporating a conventional cyclone reburner is disclosed.